Spring brake cylinder having an emergency release device

ABSTRACT

A spring brake cylinder having an emergency release device, particularly for rail vehicles, comprising: a housing; a spring piston for operating and releasing a spring brake; a normally locked, not self-locking threaded screw drive; an outer-radial sliding surface having a detent flank, the outer-radial sliding surface being an element of a rotatable part of the threaded screw drive, and the threaded screw drive having a pitch dimensioned such that the rotatable part carries out less than a complete rotation along its maximal axial adjusting stroke, and the detent flank being configured for locking the emergency release device; and a latch for interacting in a form-locking manner with the detent flank to lock the emergency release device, and for releasing the spring brake in the absence of a release pressure medium and thereby permitting axial movement of the spring piston.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a spring brake cylinder, particularly for railvehicles, having an emergency release device and having a spring pistonwhich can be moved axially within a housing. On the one hand, the springbake cylinder can be moved by means of an accumulator-type spring foroperating the brake in the event of a pressure drop and, on the otherhand, can be moved by a spring pressure chamber. The spring pressurechamber can be acted upon by a pressure medium, for releasing the springbrake, and has a normally locked, not self-locking threaded screw drivewhich is arranged in a flux or transmission of force between the springpiston and an output-side piston rod. The screw drive can be manuallyunlocked by way of a latch assigned to the emergency release device, inorder to be able to release the spring brake without any pressuremedium.

As a safety-relevant subassembly, spring brake cylinders of theabove-described type are preferably used in rail vehicle constructionfor ensuring a brake operation when there is no brake pressure. In thecase of a spring brake cylinder, the brake can be operated only by wayof accumulator-type springs so that the spring brake cylinder can beused as a parking brake of a rail vehicle in the parked condition and asa safety brake when the compressed-air system is leaking or has failedduring the driving operation.

A spring brake cylinder of the above-mentioned type is known from GermanPatent Document DE-OS 26 08 502. That spring brake cylinder consistsessentially of a cylindrical housing with an interior accumulator-typespring which, for the brake operation, in the event of a pressurefalling in the pressure chamber, acts upon the piston from the oppositeside, so that the output-side piston rod moves out. A releasing of thebrake takes place by the admission of pressure medium to the pressurechamber, in which case the accumulator-type spring is tensioned againand the piston rod moves in.

Furthermore, the spring brake cylinder has an emergency release devicefor the interruption of and the automatic returning into theabove-explained normal operating mode of the spring brake cylinder, forthe purpose of which a lockable, not self-locking threaded screw driveis arranged in the flux or transmission of force between the piston andthe piston rod. The threaded screw drive consists essentially of a partwhich is rotatable with respect to the housing and of a part which isnon-rotatable. The rotatable part may either be a nut which interactswith the piston and which is in a threaded engagement with a screwconstructed on the piston rod; or, the rotatable part may be the screwwhich will then be rotatably disposed with respect to the piston rod, inwhich case its assigned nut is non-rotatably arranged with respect tothe piston. Both carry out the same function.

During the normal braking operation—that is, when pressure is present—,the rotatable part of the threaded spindle drive is locked by way of alatch, so that a rigid flux or transmission of force is establishedbetween the piston and the piston rod in order to permit apressure-medium-operated restoring of the piston while tensioning theaccumulator-type spring in the above-described manner. The emergencyrelease device is required for releasing the brake in the event that nopressure is available for the compression of the accumulator-typespring. That is in an instance when the rail vehicle has to be moved—forexample, during a switching. In this case, the transmission of forcefrom the piston to the piston rod is manually interrupted from theoutside by the unlocking of the not self-locking threaded screw drive byway of the latch, whereby a release of the brakes can take place withoutany pressure. The return into the original operating condition of thespring brake cylinder takes place automatically when pressure isavailable again which then, as a result of the compression of theaccumulator-type spring, causes a return movement of the parts of theemergency release device.

In the prior art, this function is implemented by way of a detent pawltoothing provided at the outer radius on the rotatable part of thethreaded screw drive, which detent pawl toothing meshes with the latchin the manner of a ratchet and pawl. The detent pawl toothing permits arelative rotating movement of the rotatable part of the threaded screwdrive in only one direction, whereas the rotation into the otherdirection is prevented by the detent flanks of the toothing.

Here, the problem arises that, if the latching engages before thestoppage of the rotating parts, particularly, during a brief operationas the result of a slipping off the handle of the latch, the ratchet andpawl may be considerably worn and damaged. At extremely lowtemperatures, particularly as a result of the then reduced viscosity ofthe lubricant, the end position in the emergency-released condition maynot be reliably reached so that the brake is not or cannot be completelyreleased. This unfavorable condition will then be fixed by areengagement of the latch. In addition, the forming of the detent pawltoothing at the rotatable part of the threaded screw drive requiresfairly high expenditures with respect to the manufacturing.

The present invention relates to a further improvement of a spring brakecylinder of the above-described type such that a reliable functioning ofthe emergency release device is achieved in a simple manner.

The present invention relates to a spring brake cylinder having anemergency release device, particularly for rail vehicles, comprising: ahousing; a spring piston which can be moved axially within the housingby one of at least one accumulator-type spring for operating a springbrake in the event of a release pressure medium drop and a springpressure chamber for releasing the spring brake when the chamber isacted upon by a release pressure medium; a normally locked, notself-locking threaded screw drive arranged in a flux or transmission offorce between the spring piston and an output-side piston rod; anouter-radial sliding surface having a detent flank, the outer-radialsliding surface being an element of a rotatable part of the threadedscrew drive that rotates with respect to the housing, and the threadedscrew drive having a pitch dimensioned such that the rotatable partcarries out less than a complete rotation along its maximal axialadjusting stroke, and the detent flank being configured for locking theemergency release device; and a latch, held in contact with the slidingsurface, for interacting in a form-locking manner with the detent flankto lock the emergency release device, and for releasing the spring brakein the absence of the release pressure medium by manually unlocking thenot self-locking screw drive and thereby permitting axial movement ofthe spring piston.

According to the present invention, an avoidance of a plurality of teethon a ratchet, a wearing of the toothing as a result of an unfavorableengagement situation of the latch during the movement of the rotatablepart of the threaded screw drive is avoided. In the event of a briefoperation as a result of a slipping off the handle of the latch, thelatch always comes to rest on the sliding surface. A skipping of a toothby the latch, which would cause damage, is made impossible in that therotatable part of the threaded screw drive can maximally carry out notmore than one complete rotation. The engaging position of the latch istherefore precisely defined. This position is exclusively located in anend position of the piston after a restoring of the operability from anemergency-released condition of the spring brake cylinder.

The sliding surface of the part of the threaded screw drive which can berotated relative to the housing is constructed in the manner of a curvedpath. In this case, the detent flank constructed on the curved-path-typesliding surface preferably has an essentially radially aligned surfacein order to ensure a secure engagement of the latch. Thecurved-path-type sliding surface has a stroke difference which occurs inan interaction with the latch and that stroke difference can be utilizedfor indicating a switching condition of the emergency release device.The curved-path-type sliding surface may be provided with additionalshaped-on sections or indentations in order to be able to judge from anoutside view of different resulting stroke differences, for example, inthe emergency-released condition, the degree of release of the brake.

Within the scope of the present invention, the detent flank constructedon the sliding surface can be shaped in a groove-type manner as anindentation or in a tooth-type manner as an elevation or in anothershape permitting a detent engagement with the latch.

The emergency release device according to the present invention, whenused with spring brake cylinders, may be configured such that a part ofthe threaded screw drive rotatable relative to the housing isconstructed as a screw. The screw may be axially displaceable ordisplaced together with the piston rod and the screw may be disposed tobe rotatable about the piston rod and may interact with a nut of thethreaded screw drive. The nut may be a non-rotatable part, and may bestationarily arranged with respect to the spring piston.

As an alternative the part of the threaded screw drive rotatablerelative to the housing may be constructed as a nut. The nut may beaxially displaceable or displaced together with the spring piston andthe nut may be coaxially rotatably disposed on the spring piston, andmay interact with a screw of the threaded screw drive. The screw may bea non-rotatable part and may be stationarily arranged with respect tothe piston rod.

In the above case of the rotatable screw, a gear wheel element, whichhas an outer-radial sliding surface with the detent flank, according tothe present invention, can be stationarily fastened, at an end side, tothe screw as a separate component. On the whole, the manufacturing ofthe rotatable screw is simplified thereby and a separate exchange of aworn component can take place by demounting.

A spring arranged between the latch and the housing is preferablyprovided in order to hold, in the manner of a compression or tensionspring, the latch in a continuous contact on the sliding surface of therotatable part of the threaded screw drive. In addition to a manualoperation, it is conceivable to operate the latch against the springforce also by means of an auxiliary device in a remote-controllablemanner. As the auxiliary device, a switch-controlled electric orpneumatic actuator could be used, in which case the auxiliary energyrequired for this purpose may optionally be made available by storage ina battery or a pressure reservoir.

Other aspects and novel features of the present invention will becomeapparent from the following detail description of the invention whenconsidered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a spring brake cylinderhaving an emergency release device according to the present invention;

FIG. 2a is a top view of a schematic representation of a form-lockingengagement of a latch and gear wheel element in an operative condition,according to the present invention;

FIG. 2b is a lateral view of the engagement, according to FIG. 2a;

FIG. 3a is a top view of a schematic representation of a disengagedform-locking engagement of a latch and gear wheel element in theemergency-released condition, according to the present invention;

FIG. 3b is a lateral view of the disengagement, according to FIG. 3a.

A spring brake cylinder 50, as shown in FIG. 1, comprises a two-piece,essentially cylindrical housing 1. Within a first half 52, housing 1 hasan axially displaceable service brake piston 2. By way of an assignedservice brake pressure chamber 3, the piston 2 can be acted upon by anapply pressure medium P₁ through a connection 4 that is arranged at oron the housing 1. A braking force is transmitted to a brake linkage (notshown) of a rail vehicle (not shown) by way of an output side piston rod5 which extends out of the housing 1 in a sealed manner and is fastenedcoaxially to the service brake piston 2. A restoring of the servicebrake piston 2 takes place in a bled condition of the service brakepressure chamber 3 essentially by the force of a restoring spring 6acting between the housing 1 and the service brake piston 2.Furthermore, the piston rod 5 is equipped with a mechanical adjustingdevice 7 for compensating for a wear tolerance resulting from the wearof brake linings (not shown).

In addition to the above-described service brake piston 2, a springbrake 30 is integrated in the spring brake cylinder 50. Cylinder 50 alsohas an axially movable spring piston 8 that is arranged within a secondhalf 54 of the housing 1. On one side, the spring piston 8 can be movedby one or more accumulator-type springs 9. The springs 9 are arranged atsuch radial distances and at mutually such other distances with respectto the spring piston 8 and also interact with parts of the housing 1 inorder to automatically operate the spring brake 30 in the event of apressure drop in a release pressure medium P₂. On the other side of thespring piston 8, a spring pressure chamber 10 is situated. The springpressure chamber 10 has an assigned connection 11 for supplying therelease pressure medium P₂. The chamber 10 can be acted upon by therelease pressure medium P₂ for releasing the spring brake 30, thusrestoring the spring piston 8 against the force exercised by theaccumulator-type springs 9.

In a flux or transmission of force between the spring piston 8 and theoutput-side piston rod 5, a not self-locking threaded screw or threadedspindle drive 12 is arranged. The screw drive 12 is locked during normaloperation and can be manually unlocked by means of a latch 13 assignedto an emergency release device 60, in order to be able to release thespring brake 30 in the absence of any pressure medium P₂.

A part of the threaded screw drive 12 is rotatable relative to thehousing 1. That part may be constructed as a screw 14. The screw 14 maybe axially displaceable together with the piston rod 5 and may bedisposed to be rotatable about the piston rod 5. The screw 14 can bedisplaced by way of an outer-radial plastic bushing 15 and rotatablyguided in the housing 1.

A nut 16, may be a non-rotatable part of the threaded screw drive 12,and may be arranged stationarily with respect to the spring piston 8,and may interact with the screw 14. A rotating movement of the springpiston 8 with the nut 16 may be prevented, by a torque lock 17, whichmay interact with parts of the housing 1 in the manner of a mechanicalstop.

For locking and unlocking the threaded screw drive 12, a gear wheelelement 18 may be provided which may be stationarily but demountablyfastened to the screw 14. The gear wheel element 18 has an outer-radialsliding surface 19 with a detent flank 22 (see FIGS. 2A-3B) for thelatch 13, which interacts with the wheel element 18 and forms part of orall of the emergency release device 60. Between the latch 13 and thehousing 1, a spring 20 may be arranged which may be constructed in themanner of a compression or tension spring in order to hold the latch 13in a continuous contact on the sliding surface 19 of the gear wheelelement 18. By way of an exterior grip 21, the latch 13 can be manuallylifted off the sliding surface 19 against the force of the spring 20.

As shown in FIG. 1, the spring brake cylinder 50 is in anemergency-released condition. In this case, the spring brake 30 wasreleased without any pressure medium P₂. That was done by pulling on thelatch 13 using grip 21, which discontinues the form-locking engagementon the gear wheel element 18 and unlocks the threaded screw drive 12.The screw 14 is then freely rotatable. Thus, as a result of restoringforces, which, among other things, may originate from return spring 6,an axial moving-in (to the right in FIG. 1) movement of the piston rod 5connected with the screw 14 occurs, enabling a releasing of the springbrake 30. The pitch of the threaded screw drive 12 is dimensioned suchthat the screw 14, with the gear wheel element 18, carries out less thanan entire rotation along its maximal axial adjusting stroke.

As shown in FIG. 2a, the form-locking engagement of the latch 13 on thegear wheel element 18 takes place on a single detent flank 22 which maybe constructed to be radially or essentially radially aligned ororiented thereon, so that the threaded screw drive 12 is locked. All orpart of a circumferential surface of the gear wheel element 18 may beconstructed as a uniform or non-uniformed curved path 19. In the lockedcondition shown in FIG. 2a, the gear wheel element 18 is in an axial endposition in which a form-locking interaction with the latch 13 is stillensured. In this locked condition, a normal braking operation can takeplace, during which operation an axial displacement occurs (see FIG. 2b)between the stationary latch 13 and the axially movable gear wheelelement 18 during a stroke movement of the piston rod 5 (see FIG. 1).

In an emergency-released condition, as shown in FIG. 3a, theform-locking engagement is discontinued between the latch 13 and thegear wheel element 18. The threaded screw drive 12 (see FIG. 1) isunlocked and the latch 13 can slide freely along the curved path 19.After the unlocking, an axial relative movement takes place between thelatch 13 and the gear wheel element 18, originating from an endposition, as shown in FIG. 3b, into the position shown in FIG. 2b. Thatoccurs because of the axial moving-in movement of the piston rod 5together with the screw 14. When pressure medium P₂ is available again,a release stroke of the spring piston 8 is automatically carried outwhile the accumulator-type springs 9 are compressed. In that case, arotating back (to the right on FIG. 1) of the unlocked screw 14 with thegear wheel element 18 fastened or connected thereon takes place untilthe latch 13 arrives again in a form-locking engagement with the detentflank 22. Thus, the locked condition of the threaded screw drive 12 isreestablished. A normal braking operation will now be possible again.

The present invention is not limited to the above-described preferredembodiment. On the contrary, modifications thereof are conceivable. Forexample the present invention is not limited to an embodiment with arotatable screw and a nut which is non-rotatable with respect thereto. Ause is also conceivable in the case of a reverse principle of arotatable nut with respect to a non-rotatable screw.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that this is done by way ofillustration and example only and is not to be taken by way oflimitation. The spirit and scope of the present invention are to belimited only by the terms of the appended claims.

We claim:
 1. A spring brake cylinder having an emergency release device,particularly for rail vehicles, comprising: a housing; a spring pistonwhich can be moved axially within the housing by one of at least oneaccumulator-type spring for operating a spring brake in the event of arelease pressure medium drop and a spring pressure chamber for releasingthe spring brake when the chamber is acted upon by a release pressuremedium; a normally locked, not self-locking threaded screw drivearranged in a transmission of force between the spring piston and anoutput-side piston rod; an outer-radial sliding surface, of theemergency release device, having a detent flank, the outer-radialsliding surface being an element of a rotatable part of the threadedscrew drive that rotates with respect to the housing, and the threadedscrew drive having a pitch dimensioned such that the rotatable partcarries out less than a complete rotation along its maximal axialadjusting stroke, and the detent flank being configured for locking theemergency release device; and a latch, of the emergency release device,held in contact with the sliding surface, for interacting with thedetent flank to lock the emergency release device, and for releasing thespring brake in the absence of the release pressure medium by manuallyunlocking the not self-locking screw drive and thereby permitting axialmovement of the spring piston.
 2. The spring brake cylinder according toclaim 1, wherein the sliding surface is constructed as a curved path. 3.The spring brake cylinder according to claim 2, wherein the detent flankis an essentially radially aligned surface.
 4. The spring brake cylinderaccording to claim 2, wherein a switching condition of the emergencyrelease device is indicated by a stroke difference that occurs in aninteraction of the latch and the curved-path-shaped sliding surface. 5.The spring brake cylinder according to claim 1, wherein the detent flankis shaped in one of a groove-type manner as an indentation and in atooth-type manner as an elevation.
 6. The spring brake cylinderaccording to claim 1, wherein the rotatable part of the threaded screwdrive is constructed as a screw which is axially displaceable togetherwith a piston rod and which screw is disposed to be rotatable about thepiston rod, and which screw interacts with a nut, as a non-rotatablepart of the threaded screw drive, and which nut is stationarily arrangedwith respect to the spring piston.
 7. The spring brake cylinderaccording to claim 6, wherein a gear wheel element is stationarily butdemountably fastened to the screw, and which gear wheel element includesthe outer-radial sliding surface with the detent flank, all interactingto form a part of the emergency release device.
 8. The spring brakecylinder according to claim 6 or 7, wherein the screw is displaced by anouter-radial plastic bushing and is rotatably guided in the housing. 9.The spring brake cylinder according to claim 1, wherein the rotatablepart of the threaded screw drive is constructed as a nut which nut isaxially displaceable together with the spring piston and the nut iscoaxially rotatably disposed on the spring piston, and interacts with ascrew, as a non-rotatable part of the threaded screw drive, and whichscrew is stationarily arranged with respect to the piston rod.
 10. Thespring brake cylinder according to claim 1, wherein a spring is arrangedbetween the latch and the housing and is constructed as one of acompression and tension spring holding the latch in continuous contacton the sliding surface.
 11. The spring brake cylinder according to claim1, wherein the latch is remote-controlled by an auxiliary device.